1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device including an inductive load driving circuit.
2. Description of the Related Art
In recent years, downsizing of electronics and reducing power consumption therein requires downsized semiconductor devices mounted thereon with reduced power consumption and increased operation speeds. For example, a semiconductor device for power supplies and motor drivers has been downsized by containing a power transistor therein and packaging it in a small package. Alternatively, the absolute value of each bias current in analog circuits for controlling the power transistor has been lowered to achieve reduced power consumption.
If such the semiconductor device containing the power transistor therein drives an inductive load such as a coil and a motor, the control circuit may malfunction under the influence of a parasitic transistor. As described above, the absolute value of the bias current in the control circuit is reduced for achieving reduced power consumption in the semiconductor device while the output current capability of the power transistor is made higher as a technical trend. In a word, the semiconductor device increasingly tends to easily malfunction in the future under the influence of the parasitic transistor at the same level. For example, as described in JP 2001-77682A, a guard ring layer connected to the ground potential is formed on the same semiconductor substrate to suppress the influence of the parasitic transistor.